1. Field of the Invention
The chemically bonded chrome-magnesia refractories of this invention have use in the construction of furnaces and vessels for the manufacture of steel, cement, copper and so on.
2. Description of the Prior Art
Although a complete preliminary patentability search has not been conducted, there are patents known to be relevant to chemically bonded brick and, for that matter, to direct bonded brick which might have some bearing on these disclosures. Generally, representative United States patents disclosing chemically bonded brick are Woodhouse et al. U.S. Pat. No. 3,475,188; Davis et al. U.S. Pat. No. 3,479,194; and Farrington et a l. U.S. Pat. No. 3,615,776. United States patents disclosing direct bonded brick are Wright U.S. Pat. No. 3,715,223; Farrington et al. U.S. Pat. No. 3,829,541; Davis U.S. Pat. No. 3,852,080; and Farrington et al. U.S. Pat. No. 3,864,136.
The disclosures of the Wright U.S. Pat. No. 3,715,223 are of interest. This patent claims a fired or direct bonded brick. Some of the ingredients and ratios, however, approach those disclosed herein. Wright, for example, discloses a ratio of magnesia to chrome of 80 to 20 and 40 to 60; as to the fineness of the chrome ore, Wright contains one example wherein 69% of such ore passes a 28 mesh screen. The Wright patent also indicates a lime-silica ratio of 1.5 to 2.5; such patent also calls for a silica content of the batch to be 0.3 to 2. Finally, the Wright patent indicates that 10% of the tempering liquid, which is itself 2-4 parts, should be calcium nitrate, and/or that calcium nitrate (calculated as CaO) should be 1.5-2.5 of the total SiO.sub.2 content of the batch.
Although the Wright patent claims a fired or direct bonded brick, the Summary of the Invention of that patent indicates that benefits may be detected in the unfired shape and that the method taught could be used to produce "improved" chemically bonded refractory. The Wright patent, however, does not suggest that the firing step of its disclosure should or could be eliminated and the patent does not suggest that the chemically bonded refractory possibly obtainable would be so "improved" that it could be used in place of direct bonded or fired brick.
The instant invention taught in this application resides in a chemically bonded brick capable of being used under severe high temperature application, such as, for example, in the construction of open hearth furnaces for steel making, wherein operating temperatures may be in the range of 2800.degree. F. to 3100.degree. F. (1540.degree. C. to 1705.degree. C.). Such a brick may also incorporate metal elements which will at least be present as such during initial service within an actual furnace so as to reinforce the "green" chemically bonded brick during initial firing of the furnace.
Wright neither teaches or suggests the making and composition of a chemically bonded brick that could be used under such severe high temperature conditions, nor does Wright teach a chemically bonded brick which includes internal metal elements.